Cervical cancer is considered as the most common cause of cancer in women related to female genitals. Cervical cancer occurred more likely in women at the age group between 40 and 55, followed by the age group between 60 and 69. The risk factors of cervical cancer, in the pathogenesis, may include early marriage and child-bearing at a young age, having many sexual partners, and more importantly infection through sexual intercourse with certain types of virus, such as human herpesvirus II, human papillomavirus and human cytomegalovirus, particularly human papillomavirus types 16 and 18 (HPV 16 and HPV 18). Cervical cancer typically develops over 10 to 20 years or even longer, through chronic cervicitis (especially cervical erosion), cervical squamous epithelial dysplasia, carcinoma in situ to invasive cancer.
The morbidity and mortality of cervical cancer are substantial, and, for example, an estimated over 100,000 new cases of cervical cancer occurred each year in China. An estimated over 200,000 deaths from cervical cancer occurred each year globally. Among the young women aged 25 to 45, cervical cancer is the second-most common cause of death from cancer. Due to increasingly more relaxed attitude on sexual activities among women, the incidence of cervical cancer are gradually moved towards younger ages, which may be related to HPV infections and uncontrolled sexual activities, through precancerous changes leading to cervical cancer.
Preventive measures are still globally the most common approach to deal with cervical cancer, such as early treatment of HPV infection or direct injection of HPV vaccine for the prevention of cervical cancer. The HPV vaccines, however, are often too expensive, and treatment of HPV infection may be ineffective due to a delayed finding of the infection, which may be an important reason that the cervical cancer incidences caused by HPV infection remain high in China. Further, cervical cancer is still treated mainly through surgical and chemotherapeutic treatments, which may cause great harms to the body. The treatment of cervical cancer varies worldwide, and, as a result, the recovery rates of cervical cancer differ in various countries, for example, more than 60% in developed countries, and less than 40% in developing or underdeveloped countries, with the overall ratio maintained at the average of more than 50%.
Nano-silver is a type of nano materials. Elemental metallic silver or some silver compounds are treated in physical or chemical method to make nano-scaled metallic silver powder. Due to a high surface area, metallic silver shows some new functions in terms of physical and chemical properties, especially the antibacterial properties. Currently on the market, nano-silver powders are often prepared via chemical methods in varied particle sizes and shapes and with different impurities, and thus it would be difficult to determine the purity, consistency and stability and further the safety of the material. Most of the nano-silver products provided by the manufacturers are of nano-silver being attached on fabric materials to form antibacterial fabrics. Such antibacterial fabrics are then used for various antibacterial purposes, which are of low-level applications. A few domestic manufactures and some foreign manufacturers began to study more precisely the antibacterial properties of nano-silver materials and to develop better performance of nano-silver materials without adversary effects on human body to be used in production of medicines and medical devices, such as sterilization, antibacterial and antibacterial products, masks, gel and suppository.
In recent years, the rapid development of nano-technologies promoted the application of nano materials in the medical field. In the family of the nano materials, nano-silver is a type of elemental silver made with nano structure and high purity, and thus is special in biological functions. High-purity elemental nano-silver has been used in malignant tumor cells in vitro with anti-cancer effects. Also, it was reported that nano-silver is useful in cancer's early stage diagnosis and prognosis monitoring. In the National Institution of High Energy Physics, the scientists for nano biological effects recently discovered that nano-particles after chemical modification demonstrated relatively high efficiency on inhibition on tumor growth without killing the cells directly, which made the immunity enhanced in the mice with tumor and also showed almost no toxicity. It is rather different from traditional antitumor drugs. Experiments indicated that high-purity nano-silver of certain particle sizes and at certain concentrations may achieve the above result, which is desired for the treatment of cancers (Nano Letters, 2013). It is an interesting result for the scientists that such nano-particles need not directly kill the cells, and their distribution in the tumor tissue can be very low, only one over one hundred thousand, for example. Such results suggest that the inhibitory effect of the nano-particles is achieved not by direct killing of the cells and therefore there may be some other unknown anti-cancer mechanisms for further investigation. Nano-technology shall facilitate the discovery effort of new anti-cancer drugs.
Currently, most of the clinical used anti-tumor drugs are highly toxic for killing cells, while killing the tumor cells the drugs also seriously damage the normal cells. The above-mentioned studies avoided such toxicity problem, and thus were considered as of a new approach for the treatment of cancer with high efficiency and low toxicity. However, the above studies used chemically modified nano-particles, which may have drug safety concerns, and further there were no any reports regarding whether the cell killing effect is due to the chemical modification or the nano-particles themselves.
As discussed below, the inventors applied high-purity elemental nano-silver in malignant tumor cells in vitro, and found the anti-cancer effect thereof. The inventors discovered an anticancer nano-silver composition with high purity, high efficacy, high stability and low concentration, and established a drug system of highly dispersible, highly stabilized and readily releasable for drug dispersion, preservation and release and further a method of preparation of such composition.